1. Field of the Invention
The present invention relates to a flange for optical flame observation in a gas turbine. The flange comprises at least one bore for optical observation, in which bore there is arranged at least one pane for separating the flame-side space, which is in substantially direct communication with a combustion chamber in which the at least one flame that is to be monitored is arranged, from the outside space, from which the observation of the at least one flame can take place.
2. Brief Description of the Related Art
For safety reasons, the flames in the combustion chamber of a gas turbine have to be observed and monitored. Inter alia in the case of annular combustion chambers, in which to a certain extent there is a single, encircling flame supplied by a plurality of burners arranged over the circumference of the circle, this monitoring and observation is carried out, for example, by at least one observation tube being passed through the housing of the gas turbine to the outer side of the gas turbine. The tube leads through cavities which are arranged in the housing and are used, for example, to supply cooling air, additional combustion air or to accommodate fuel supply lines, etc. The tube is usually open toward the combustion chamber, i.e. the pressure prevailing in the tube usually substantially corresponds to the pressure in the combustion chamber, and the temperature in the tube is likewise usually in the region of the temperature in the combustion chamber, although on account of weak convection in the tube a decreasing gradient is established toward the outer side of the gas turbine with respect to the temperature.
Observation means in the form of flame monitors with optical detectors, which allow automated and continuous observation and monitoring of the flame activity, are usually arranged on the outer side of the gas turbine. These observation means are arranged outside the gas turbine, i.e. substantially at room temperature and standard pressure, on the one hand in order not to apply excessive thermal and mechanical loads to these observation means, and on the other hand to make them easier to exchange and easier to carry out maintenance work on. In order accordingly to seal the tube with respect to the outer side, where substantially room temperature and standard pressure prevail, without at the same time impairing the optical path for observation, it is customary to provide at least one suitable pane, i.e. a pane which does not interfere with the optical path of flame observation, which pane is fitted either at the end of the observation tube or in a flange placed onto the observation tube. On account of the high temperature differences and pressure differences between the interior of the observation tube and the surroundings of the gas turbine, this pane has to satisfy high mechanical demands and has to be well sealed. For this purpose, it is customary for the at least one pane to be fitted into the flange, i.e. for example welded into the flange.